1. Field of the Invention
The present invention relates to an optical lens, and more particularly, the present invention relates to an optical lens for a light-emitting device.
2. Description of the Prior Art
The lighting characteristic of the street lamp will influence the sight of the person who takes way during the night, so the governments of various countries all have relevant regulations to the illumination intensity and structure of the street lamp, so as to protect the person who takes way. Currently, light-emitting diodes (LEDs) have been applied to provide the light source of the street lamp. Generally speaking, the package structure of an LED is disposed inside the lampshade of the street lamp, and the LED is covered by an optical lens for refracting light emitting from the LED to form the light field 12 as shown in FIG. 1. In the prior art, the light field 12 formed through the optical lens locates along the direction of the central optical axis of the lens, and the light field is about symmetrical.
Because the light field formed through the optical lens in the prior art merely locates along the direction of the central optical axis of the lens, in order to make the light field projected on the road surface to provide illumination for the person who takes way, the lampshade 10 of the street lamp 1 is usually lifted up to make the central optical axis of the lens towards the road surface such that the light field can be projected on the road surface. Please refer to FIG. 1 which illustrates the schematic diagram of the street lamp 1 in the prior art.
However, the lifted up lampshade 10 often introduces glare phenomenon to the person who takes way affecting road safety. Hence, the street lamp in the prior art still needs improvements regarding the road safety for the person who takes way